//占用1个字节，读取boot2到0x7e00处

	.set BOOT2_SIZE,4 #BOOT2_SIZE默认4字节
	.set BOOT2_START,0x7e00  #boot2  位于内存0x7e00处
	.code16
	.global _start
_start:
/*
 * BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
 *	Call with	%ah = 0x2
 *			%al = number of sectors
 *			%ch = cylinder
 *			%cl = sector (bits 6-7 are high bits of "cylinder")
 *			%dh = head
 *			%dl = drive (0x80 for hard disk, 0x0 for floppy disk)
 *			%es:%bx = segment:offset of buffer
 *	Return:
 *			%al = 0x0 on success; err code on failure
 */
	xor %ax,%ax
	movw %ax,%es
	movb $(BOOT2_SIZE), %al
	movb $0, %ch
	movb $1,%cl
	movb $0,%dh
	movb $0x80,%dl

	movw $0x7e0,%bx
	movb $0x2,%ah
	
	int $0x13
	movw $0x7e00,%bx
	jmp  *%bx

 .org 0x1be
 .word 0xaa55	

